Stoker control



May 30, 1933- P. F. sHlvEs 1,911,773

STOKER CONTROL Filed May 6, 1931 4 Sheets-Sheet l 2*, :lwucm-toz attenua@ May 30, 1933 v P. F. sHlvERs l. 1,911,773

sTKER CONTROL Filed May 6, 1931 4 Sheets-Sheet 2 gwwntoc May 30, 1933. P` F SHNERS 1,911,773

STOKER CONTROL Filed May 6, 1931 4 Sheets-Sheet 3 P. F. SHIVERS STOKE@ CONTROL May 30, 1933.

Filed May 6, 1931 4 Sheets-Sheet 4 u m ,W QN 4 MXN H xNwN QN f v J 4%? NWN NWN .QN wN f 5 NMN N m WN @NN HH .H Il m .RN @NN v mwN WN. QNN m l Q j @WN JWN QWN NM mu MNA? 51 NNN /NN www P6721/ Ff JMJ/e217,

fed furnaces by Patented. May

g UNITED s'rAfras PATENT ori-fica PAUL I'. SHIYEES, Ol WTABABH, INDIANA, ASSIGNOR TO MINNEAPOLIS-HONEYWELL REGULATOR OOHPLNY, F MINNEAPOLIS, MINNESOTA, A CORPORATION OF DEI4L WARE STOXER Application led lay The object of my invention is to provide an improved control apparatus for stoker 'means of which successive charges of fuel will be delivered to the furnace in response to temperature demands of the space to be heated, the periodicity and extent of such fuel delivery riods being vgriable, and by means of whic fuel charges o matically delivered to the furnace, in the absence of temperature demand in the space to be heated, at a predetermined interval of time next following a preced' fuel charge whether such preceding fuelc arge was in response to room temperature demand or in response to lapse of-^t1me in the absence of room temperature demand.

The accompanying drawings illustrate my invention:

Fig. 1 is an eleva-tion 'in partial vertical section of a special switch-controlling unit, the details of construction of which are not ori 'nal with me.

ig. 2 a fragmentar section in the plane of the rotor shaft of t c motor;

Fig. ,3 a section on line 3-3 of Fig. 1;

Fig. 4a section on line 4--4 of Fig. 1;

Fig. 5 a section on line 5-5 of Fig. 3;

Fi 6 a fragmentary section inthe planeo'f Fig. 3 with the latch mechanism inv the positions assumed when the driving pawl is held retracted;

Fi 7 a fragmentary section on line 7-7 of Fig. 1; the partsvbeing shown in an advanced position.

Fig. 8 a fragmentary section on line 8-8 ofFig. 1;

Fig. 9 a section on line 9--9 of Fig. 1;

and

Fig. 10 a wiring diagram.

. In the drawings 10 indicates a suitable supporting frame in which is mounted a power-receiving shaft 11 and a power delivery shaft 12 with an intermediate speedreducing train 13 of any desired character. Shaft 11 is conveniently the rotor shaft of an electric motor 14 and this shaft carries a flange 15 upon which are pivoted two arcshaped frictionlshoes `16 which lie within a stationary shell 17. The shoes `16 are so redetermined amounts may be auto- CONTROL 1931. Serial No. 535,406.

formed that, when shaft 11 is rotating .at full speed, said shoes will hug the shaft but, as the speed of shaft 11 drops below normal, said shoes, as they pass beneath the shaft, will drag upon the inner surface of the stationary shell 17 which encloses the shoes, said shoes thus having, a braking effect to hasten stoppage of the motor.

The power delivery shaft 12 carries a pinion 20 which meshes with a gear 21 journaled upon a stud pin 22 supported upon frame 10 and gear 21 carries a hardened tchet ring 23 provided with ratchet teeth J ournaled uponstud 22 is a which is to bel automatically oscillated through various arcs from an initial osition by the mechanism now to be descrlbed. Secured to that end of sleeve 25 adjacent sleeve 25 gear -21 is a plate 26 having a pin 27 pro- 'l0 )ected into a spr-ing chamber 28 formedin gear 21. Pin 27 'forms the anchorage for one end of a, volute spring 29 nested in chamber 28 and having its inner end atu tached, at 30, to stud22..

In order to set spring 29 at any desired tension stud 22 is journaled, at 31, in frame 10 and may be held in any desired position of angular adjustment by nut 32 threaded gagement with lever 38, being normally yieldingly retained in engagement with lever 38 by a spring 41 anchored at 42 on lever 38 and engaging lever 37 at 43. Lever 37 is provided with a latch linger 44 with which cooperates a shoulder 45 of a latch lever 46 pivoted at 47 on plate 26. Also pivoted at 47 is a latch lever 48 having a latch shoulf I 39. Lever 37 isq der 49 adapted to cooperate withI finger 39 of lever 38. Lever 461s urged in a counter clockwise direction (Fig. 3) relative to lever 48 by a spring s, one end of which is anchored at 50 on latch 46 and the other end of which is anchored on a pin 51 on latch lever 48, said pin 51 serving as a stop to limit counter-clockwise movement of lever 46 relative to lever 48. Latch lever 48 is provided with a linger 52 which overlies, and under some conditions is adapted to enage, lever 38, in one direction,` to shift'said ever in a` clockwise direction. Lever 48 is yieldingly urged in a clockwise direction by a spring 54 anchored at 55 yon plate 26. Lever 38 is yieldingly urged in a clockwise direction by a spring 56 anchored at 57 on plate 26.

When pawl 36 is in effective position relative to the ratchet teeth 24, the parts are in the positions shown in Fig. 3, at which time finger 39 of lever 38 is restrained in itsl uppermost position by resting upon shoulder 49 of lever 48; finger 44 of lever 37 lies under lever 46 with its end free from shoulder 45 of lever 46; and finger 40 of lever 37 lies in engagement with lever 38.

J ournaled upon sleeve 25 is aratchet disc 60 provided with a segmental series of ratchspacers et teeth 61. Disc 60 is provided with pin 62 (Fig. 4) which is projected into the plane of lever 48 beyond its axis so as to be capable of swinging lever 48 in a counter-clockwise direction. Ratchet disc 60 is also rovided with a pin 63 pro'ected into the ane of lever 38 and adapte to move said ever, against the action of spring 56, in a counter-clockwise direction.

The pin 62 is carried by a projecting finger 60 of disc 60 and projected into the path of movement of this finger is a stationary finger 65 carried by the frame 10 to limit the movement of disc 60 in a clockwise direction.

Movement of disc 60 in a counter-clock- Wise direction is limited by a stationary pin 66 carried by frame 10.

Splined upon sleeve 25 is a sleeve 70 uponl which are sleeved plurality of switchactuatin cams 71, 72, 73, with interposed 74 and held in relative angular ad- Justment by a nut 75 threaded upon the outer end of sleeve 70. The locking nut 76, threaded upon the outer end of sleeve 25 serves to hold-sleeve 70 in place against shoulder 77 of sleeve 25 andalso serves as a locking nut for the nut 75.

A spring 79, anchored at one end on Ein 80 carried by sleeve 70 -and at the ot er end on pin 81 carried by ratchet disc 60, serves to normally hold pin 62 in engagement with lever 48.

'In Fig. 3 the parts are shown in the positions occupied when disc 60 has been advanced nearly to the limit of its forward stroke, pin 62 being at that time 1n engage- Further advancement, in clockwise direction, of gear 21 and plate 26 will, because of the engagement of pin 62 with lever 48, cause said lever to swing upon its .pivot against the action of spring 54 so as to wit drawshoulder 49 from beneath fin er 39 oflever 38, whereupon, spring 56 wil swing lever 38 clockwise to initial position.

The left hand-farm of leve 46, during the major portion of the above-mentioned movement of lever 48 is obstructed by finger 44 of lever 37. When shoulder 49 is fully retracted from finger 39 of lever 38, said lever will be released and swung in a clockwise direction by spring 56, the lever 38 positively retracting pawl 36 from the ratchet teeth 24, at the same time shifting finger 44 to the left to permitk shoulder 45 of lever 46 to drop down behind it to definitely lock pawl 36 in a retracted position relative to the ratchet teeth.

Plate 26 is thus released from driven connection with gear 21 and spring 29 .acts to return said plate, and the connected cam sleeve unit, to initial position finger 60 coming into engagement With stop pin 66 and the inner end of lever 38 coming into engagement with stop pin 63, shortly after finger 60 has been stopped by finger 66. Theengagement of lever 38 with stop pin ment with pin 65.

63 swings said lever in a counter-clockwise y 92. This pawl is normally urged inwardly to engagement with the ratchet teeth 61 of disc 60 by a spring 93 and this springurged movement relative to lever 92 is hmited by stop pin 94 carried by lever 92.

The other end of lever 92 1s connected by link 95 with a lever 96 which carries the armature 97 of a relay 98 which, when energized, serves to drive pawl 90 in a direction to angularly shift disc 60 a distance sufficient to cause its in 62 to actuate level' 48 in the same way t at said lever is actuated when finger 60 is stopped by stop finger 65, so as to retract paw 36 from teeth 24.-

to swing to locking Armature 97 is normally biasedaway from l nainvve teeth 61 is such thatthe initial end of this series of teeth does not come opposite awl Y 90 until the advancement of the disc 60 rom its initial 'tion has continued for a predetermin period, say about ten minutes if the gear train 12 is such that the total movement of disc will require a period of an hour, more or less.

In order that the pawl- 90 may not offer frictional ,resistance to forward movement of disc 60, it is held normally retracted from the ratchet teeth by a stop pin 99.

The one-way engagement between levers 37 and 38 permits the necessary freedom olf ratchet 36 relative to teeth 211. l

Failure of any one of the springs would not permit damage of the apparatus due to an excessive forwarding action of the ratch- 2@ et drive because, linger 60' being positively driven against stop pin 65, pin 62, engaging lever 48, will swing it counter-clockwise to drive its linger 52 against lever 38, which, moving clockwise and engaging finger l10, will retract pawl 36 from ratchetteeth 21 so that the motor may proceed without damage to the apparatus. 11 sprin 29 has become inedective the parts willg remain in their most advanced position; if spring 11 has become inedective, the coaction of pawl 36 with teeth 241 through said range will be inedective; il either or springs 51 and 56 has become ineffective there wili be merely a delayed coactien between levers 38 and 48.

The mechanism which has been described above is conveniently supported upon a balielite base 100. Mounted upon base 100 below the cam shaft is mounted a shaft 101 upon which` are supported three springurged rocking brackets 102, 103 and 101 carrymg fingers 105, 106 and 107 arranged to be contacted respectively by the cams 71, 72 and 73. Bracket 102 carries a balrelite arm 108 to which is secured a s ring terminal 109 arranged, when permitte by cam 71, to contact with the terminal 110-carried by suitable insulating support. Bracket 103 Y carries a balrelite arm 111 which carries the spring terminals 112 mnd 113, terminal 113 being projected through the body ot terminal 112, as shown in Fig. 8. 'Ehe terminale 112 and 113 are electrically-connected and are arranged to Contact, when permitted by cam 72, with terminals 111 and 115 respectively, which terminals are electrically-msulated from each other.

Bracket 101 carries a balaelite arm 116 upon which are mountedthe spring termi--l nels 117 and 118 electrically isolated from each other and arranged to contact, when permitted by cam 73, with terminals 119 and 120 respectively, the terminal 118 coming into contact with terminal 120 slightly before terminal 117 contactswith its terminal 119.

Cams 71, 72 and 733are so formedA and positioned, that, when the fly-back mechanism is in its initial position terminals 109,

112, 113, 117 and118 will be in Contact with arrangement being such that 126 contacts p with 129 when relay 98 is deenergized and 125 and 127 contact respectively with128 and 130 when the relay 98 is energized.

Turning now to the wiring diagram Fig. 10. A room thermostat R of well known form is installed in a room to be heated. This thermostat conveniently comprises a bimetallic blade 135 having contact fingers 136 and 137 electrically connected with blade 135 and arranged to contact respectively with terminals 138 and 139, 137 contacting with 139 slightly in advance of the contact between 136 and 138. Terminal 128 is connected to line wire 113.

A transformer T has its primary 110 connected by wires 111 and 142 with the line wires 1113 and 1111 respectively. The secondary 115 of transformer T has one end connected by wire 116 with one end of relay coil 98 and this wire is connected through rheostat liti-l with the Held of the timer motor 14, the other end of said field being connected by wire 147 with terminal 126 and terminal 109. 'lhe other end of the secondary 1115 is connected by wire 118 with terminal 120 and also with one terminal 119 of a temperatureresponsive circuit-controlling switch S, commonly known as a taclr control or combustion-controlled switch which is placed at a point where it will be promptly adected by combustion conditions in the furnace; the other terminal 150 of the stack control S is connected by the branched wire 151 with terminals 118, 110, 139, 115, and 129. Blade 135, and its associated Contact lingers 136 and 137, of the room thermostat R, is connected by a wire 152 with terminals 127 and 112 and 113. @ne end of relay coil 98 is connected by the branched wire 153 with terminals 130, 138 and 119. rllerminals 111 and 117 are connected by wire 154.

The Stoker motor M is connected by Wire 155 with the line wire 1114i, and by Wire 156 with terminal 125.

Diagram Fig. 10 shows the circuit condition at the time when the cam shaft 70 is in its initial, or re-cycled position, and assum' ing the room thermostat to be satisfied and through the circuit 144, 155, M, 156, 125, 128,

143. The timer motor is energized through the Circuit 145, 146, RH, 14,147, 109, 110, 151, 118, 120,148, 145, and as soon as there is a tem rature increase in the lire a parallel is esta lished through 15G-149. Adjustment of the rheostat RHV will vary the speed of the timer motor and thus change the length `of the time cycle.

Forward movement of the cams for a predetermined interval, brings cam 73 into position to first withdraw terminal 117 from terminal 119, thus opening the'initial energizing circuit of the coil 98 but not disturbing the holding circuit described above. 1f, during this interval, there has been an increase in temperature of the tire, 150 will have beenl contacted with 149, thus providing the cir- Cuit 145, 146, RH, 14, 147,109, 110, 151, 150, 149, 148, 145, to kee the'timer motor in movement. Further s ight advance of cam 7 3 moves 118 away from 120, so that, if contact at 150-149 has not been established b increase of furnace temperature, the ho ding circuits through 98 and 14 are not established and further operation of the Stoker motor and timer motor is stopped because the release of the relay 98 opens the Stoker motor circuit at 125-128 and the timer motor circuit is open at 118-120 so that further operation cannot be obtained until the fire is rekindled.

If there has been a proper 'response of stack control S to fuel delivery under these circumstances, the forward movement of the timer motor continues and fuel delivery continues until cam 72 separates 113 from 115, whereupon the circuit through the rela coil 98 is broken, the relay armature release and the circuit of motor M broken at 125-128. Further advance of the cams opens a gap at 109-110 but, the release of the relay 98 having established contact at 126-429, the timer motor continues to be energized through the circuit 145, 146, RH, 14, 147, 126, 129, 151, 150, 149, 148, 145, and proceeds to the end of its cycle where 62 causes movement of 48 (Fig. to release the snap-back mechanism, in the manner previously described to recycle the apparatus.

It will be noted that cam 73 is a short cam which serves to separate terminals 117 and 118 from their respective terminals 119 and 120 for only a short period inl a cycle and that cams 71 and 7 2 are longer cams serving to separate terminals 109, 112 and 113 from their respective terminals 110, 114 and 115 at times when terminals 117 and 118 are in contact with their respective terminals 119 129, as already stated. Terminal 112 sepa-' rates from 114 shortly before 113 separates from 115, thus avoiding any chattering.

Whenever the room thermostat R calls for heat by contacting terminals 136 and 137, with their respective terminals 138 and 139, relay coil 98 is initially energized through the following circuit: 145, 146, 98, 153, 133, 136,137, 139,151, 113,120, 143, 145 and operates to close the gaps at 127-130, and 125-128, and open a gap at 126-129, thus completing the circuit of motor M as already described. The closing of the gap at 127,-130 completes a holding circuit for the relay 98 as follows: 145, 146, 98, 153, 130, 127, 152, 135, 137, 139, 151, 118, 120, 143,

145. vEnergization of relay 98 always re- If the call for heat by the room thermo- A stat is initiated before, and continues after, cam 71 opens the circuit gap at 10Q- 110, the opening of this gap serves to stop the timer motor 14 because of the break in the circuit 145, 146, RH, 14, 147, 109, 110, 151, 150, 149, 148, 145, but, as already pointed out, the relay coil 98 being energized through a circuit controlled by the room thermostat, the stoker motor circuit through 125-'128 is preserved and fuel delivery continues until the room thermostat-is satisfied, whereupon, the relay circuit being broken, the stoker motor circuit is broken at 125 128, and the timer motor circuit 145, 146, RH, 14, 126, 129, 151, 150, 149, 143, 145, is established so that the timer motor carries 'the snap-back apparatus on to the end of its cycle.

If there is a call for heat by the room thermostat after cam 71 has opened the circuit gap at 109-110, cam 72 has opened circuit gaps at 112-114 and 113-115 and cam 73 has opened, but again closed, circuits at 117-119 and 118-120. Consequently when the room thermostatbrings both of its fingers 136 and 137 in contact with their respective terminals 138 and 139, the initial energization of 98 is accomplished through the Circuit 145, 146, 93, 153, 133, 136, 137, 139, 151, 118, 148, 145, establishing the stoker motor circuit at 125-128 and the relay holdingcircuit at 130--137- Energization of the relay causes pawl 90 to trip the snap-back "nettare i mechanism yto permit its return to initial position, thus recycling the apparatus.,

At this point we call attention to the fact that the stack control S is preferably of that well known type wherein separation of terminal 150 from 149 takes place promptly upon decrease of temperature and reestahlishment of contact is accomplished prompt ly upon increase of temperature, irrespective of absolute tem rature, so that at an early stage in each uel delivery period the element S stands guard to throw the appa ratus automatically out ofA coission if there is a' drop in temperature or there fails to be a prompt rise in temperature im ately following the beginning of each fuel delivery.

'lt will be noted therefore that the apparatus has the following characteristics:

, -So long as the room thermostat is satisfied there will be recurrent deliveries of fuel for predetermined riods' ually spaced.

Any call for eat by t e room thermostat, overlapping a timefperiod fuel delivery, results in a stoppage of the timer motor while fuel delivery persists under the call of the room thermostat until it is satisfied, whereupon the timer motor proceedsto the .end of the -c cle of the sna -back mechanism so that, in the absence o I a succeeding call for heat by the room thermostat, during the remainder of the cycle, a predetermined time will elapse before there will be another tmei period fuely delivery. v The apparatus is always (providing there is an existing fire), responsive to a room thermostat call for heat and whenever that call comes (except during the very short time when cam 7 3 is functioning to produce circuit gaps at 11'7--119v and 118-120) the sna -back mechanism is automatically recycl so that each fuel delivery, whether it be in response to lapse of time or in res use to room thermostat control, occurs at t e be ginning of the newly established timeriod cycle. Consequently each time-peri fuel delivery occurs only after the lapse of a redetermined time following the last, rece ing fuel deliverywhether that fuel delivery has been in response to lapse of time or room thermostat call.

When the apparatus. has been thrown out of commission, due to production of circuit `gaps at 117-1i9 and 11e-12e than a circuit gap exists at 149-150, the apparatus must be manually recycled and, o course, this recycling would not be accomplished until after the lire had been ice-kindled so that -150 would be contacted with 149. The manual recycling is accomplished by mani which will cause pawl to recycle the snapback vmechanism and establish a holding enerfizing circuit for ,relay 98 through 130 12?, as already described, Ewhereupon the ap- Fig. 4

paratus is put back into condition for con;

tinued automatic operation.

The .fpndamental results attainable by the operations ofthe above-described apparatus, i. e., the energization of a fuel-feeng device at irregular intervals, depending upon the needs of a space to be heated and upon the call of a timed element, by means of a circuit-controllingV element which is automatically recycled at each call for fuel, either by the time-train or by heat demand, have been accomplished by others and, there` fore, my invention resides in the provision of certain variable circuit relationships, in a recyclingmechanism of the described character, by' means of which there will he automatically established desirable holding circuits for the relay which vcontrols eneration of the fuel motor so that, an initiating. circuit having been established for the relay, in response to any call for fuel, there will also be provided a relay holding-cir-v cuit which is controlled by a contact which, itself, is inca able of coinpletin the initiat-y ing circuit, t us yinsuring relia ility of action. i i v Termsffound in the claim are defined as follows: room thermostat, a` dua1circuit thermallymesponsive switch having a blade contacting two independent contacts in succession and bridging the same; lirst timercontrolled Iewitc a dual-circuit mechanically operated switch having two blades contacting two independent contacts in succession; second timer-controlled switch, a dual-circuit mechanically operated switch having a blade contacting two independent contacts in succession and bridging the saine; third timer-controlled switch, a single-circuit mechanically-operated switch; y

timer-motor, an electric motor actuating the three mechanicall combustion-controllo switch, a single'- point, thermall -responsive switch alternately makin t an breaking contact upon reversals o temperature; relay, an electrically-operated switch having three electrically-independent contacts controllin three circuits two of whichvare contacted; when the relay coil is. energized and the other contacted when the relay coil is de-energized; rec cling driving train, a driving connection tween the timer motor and the switches actuated thereby such that the switch-actuating mechanism may be automatically returned to initial position at the endy of a predetermined 'stroke or from intermediate positions.v

l claim as my invention:

l. A Stoker-controller comprising an electrie -timer-motor, an energy source, a room thermostat, a combustion-controlled switch, a relay embodying three electrically-indendent switch elements two contacting and the other breaking upon relay energizatilon,

operated switches;

an energizin circuit for an electric motel` to be controlle a rst timer-controlled switch, a second4 timer-controlled switch, a third timer-controlled switch, a recycling driving train between the timer-motor and the first, second and third timer-controlled switches, and circuit connections between the several parts whereby completion of circuits through the room thermostat energizes the relay to recycle the said first, second and third switches, operation of the timer motor manipulates its switches to cause timer motor continuance or stoppage depending upon condition of the combustion-controlled switch and timer-motor `stoppage if and while the room thermostat calls for heat beyond normal time call, and upon any energization of the relay a relay-holding circuit is thereupon established through contacts actuated by the timer motor which themselves cannot serve to establish initial relay energization.

2. A Stoker-controller comprising an electric timer-motor, an energy source, a room thermostat, a combustion-controlled switch, a relay embodying three electrically-independent switch elements two contacting and the other breaking upon relay'energization, an energizing circuit for an electric motor to be controlled, a first timer-controlled switch, a second timer-controlled switch, a third timercontrolled switch, a recyclin driving train between the timer-motor and the first, second and third timer-controlled switches, and electrical connections between relay coil, sourceroom thermostat, first and second timer-controlled switch and one relay switch, and electrical connections between room thermostat, iirst and second timer-controlled switch, combustion-controlled switch and source, and electrical connections between source, timer-motor, third timer-controlled switch, one relay switch, room thermostat, first and second timer-controlled switch and combustion-controlled switch, substantially as and for the purpose described.

3. A Stoker-controller comprising an electric timer-motor, an energy source, a room thermostat, a combustion-controlled switch, a relay embodying three electrically-independent switch elements two contacting and the other breaking upon relay energization, an energizing circuit for an electric motor to be controlled, a rst timer-controlled switch, a second timer-controlled switch, a third timer-controlled switch, a driving lay switch,

timer-motor manipulates its switches to cause timer-motor continuance or stop age depending upon condition of the com ustion-controlled switch and timer-motor sto age if,and while the room thermostat cal s or heat beyondnormal time call and upon any energization of the relay a rela holding-circu1t is thereupon established t rough contacts actuated by the timer-motor which themselves cannot serve to establish initial relay enerzation..

a. A stoer-controller comprising an electric timer-motor, an ener source, a room thermostat, a combustion-controlled switch, a relay embodying three electrically-independent switch elements two contacting and the other breaking upon relaly energization, an energizing circuit for an e ectric motor to be controlled, a irst timer-controlled switch, a second timer-controlled switch, a third timer-controlled switch, a driving train between the timer motor and the three timercontrolled switches capable of driving said switches through their cycles and to initial position and electrical connections between relay coil, source, room thermostat, iirst and second timer-controlled switch and one relay switch, and between room thermostat, first and second timer-controlled switch, combustion-controlled switch and source, and electrical connections between source, timermotor, third timer-controlled switch, one reroom thermostat, first and second timer-controlled switch and combustion-controlled switch, substantially as and for the` purpose described.

In witness whereof, I have hereunto set my hand at Wabash, Indiana, this 16 day of April, A. D. one thousand nine hundred and thirty-one.

PAUL F. S L VERS.

train between the timer motor and the three x timer-controlled switches capable of driving said switches through their cycles and to initial position, and circuit connections between the several parts whereby completion of circuits through the room thermostat energizes the relay to recycle the said first, second and third switches, operationof the CERTIFICATE 0I." CORRECTION.

Patent No. 1,911,773.

'PAUL F. SHIVERS.

It is herehy certified that error appears in the printed specification of the above numbered patent requirngcorrection as follows: Page 6, line 93, claim 4, after "and" insert the words "electrical connections"; and that the said Letters Patent shouldL be read with this correction therein'that the same may conform to' the-record ofthe case in the Patent Office.

Signed and sealed this 1st day of August, A D. 1933.

M. J. Moore.

(Seal) May 30, i933.

" Acting Commissioner of Patents. 

